The role of a spy has changed over the centuries, and as our wars and military budgets have grown, the art of spying has evolved. One of the reasons spies have gotten away with all that skulking around is spy gear; they've had some cleverly designed items to accomplish their missions. They've used cameras disguised as cigarette cases to photograph documents, tiny deadly guns that can fit into the palm of the hand and everyday items like shaving cream cans with secret compartments to hide messages.

Given the secret nature of espionage, it can take years — and sometimes decades — for confirmed evidence of spy gear to make its way into the public domain, so many of the crazy gadgets we list here date back to World War II. Perhaps someday our grandchildren will read about the spy gear that's in use today.

Here are four clever spy gadgets worth mentioning:

Monopoly games with secret maps and supplies for escape

In WWII, agents of the British secret service unit MI9 oversaw the development and distribution of special-edition versions of the board game Monopoly to British POWS held in German camps. These boxes were secretly packed with maps, compasses and other tools that would be helpful to a solider who wanted to escape. The games were one of the items that were permitted by the Germans from humanitarian groups like the Red Cross. Each of the special-edition games concealed silk maps of the areas around known German POW camps, compasses, and real bank notes mixed in with the game money. British pilots were told to look for the games in the event of their capture, and some estimate that the games' secret tools were used by thousands of POWs over the course of the war. Sadly, all the special edition sets known to exist were destroyed after the war.

Acoustic Kitty

Operation Acoustic Kitty was an attempt by the CIA in the 1960s to use cats to covertly record Russian agents and government officials. The plan called for agent cats to be outfitted with microphones transmitting through antennas implanted in the cats’ tails.

The CIA spent millions of dollars refining the technology before the agency felt ready to deploy an acoustic cat on a real mission. For the trial run, agents released one of their modified cats into a park in Washington, D.C., with the hopes of recording two men sitting outside the nearby Soviet compound. Instead, the cat immediately ran away, dashed into the street, and was struck and killed by a taxi. The CIA scrapped the project not too long after the first disastrous run.

Fake poop

During the Vietnam War, an American intelligence agent had the idea of hiding seismometers in fake poop to scatter along the Ho Chi Minh trail. The fake poop would be left alone by passing Viet Cong soldiers and would detect and transmit the vibrations caused by their passage back to American agents, giving them information about the size and frequency of troops along the trail. The idea of fake poop proved to be so successful that it was expanded and used to pass information between sources and their handlers. Messages would be placed in hollowed out pieces of fake poop and left to be picked up at a later time by the intended recipient.

It's brilliant logic. When was the last time you picked up a piece of poop that you saw on the side of the trail — unless, of course, you were picking up after your dog?

Poison-pellet umbrella

Georgi Ivanov Markov was a Bulgarian writer and dissident who defected from his country in 1969. After settling in the West, Markov worked as a journalist for outlets like the BBC World Service and Radio Free Europe, using his influence to criticize the communist Bulgarian government. His campaign was successful, and he was marked by the government for assassination.

After two failed attempts on Markov's life, the Bulgarian secret police were finally able to kill him after agents used an umbrella modified with a sharp tip filled with ricin poison to stab him at a London bus stop. Markov reported feeling a small sharp pain on the back of his leg while standing at the stop and turning to see a man with an umbrella rush away and flee in a taxi. He continued on to work, but was later admitted to the hospital with a fever. Three days later he was dead. During an autopsy at Scotland Yard, investigators found a small metal poison pellet that had been injected with the umbrella.

KGB defectors later verified the details behind the operation, though no one was ever prosecuted for the crime.